...Emanuel D. Kästle; Michael Weber; Frank Krüger AbstractWe use recently deployed seismological arrays in Africa to sample a 2D cross section through the mantle down to the core–mantle boundary (CMB). By making use of travel‐time residuals of S, ScS, and SKS phases, a new shear‐velocity model...

...Henrik Friis AbstractMoskvinite-(Y), Na2K(Y,REE)Si6O15, is a rare mineral, which until now has only been described from its type locality Dara-i-Pioz, Tajikistan. At Ilímaussaq moskvinite-(Y) was discovered in a drill core from Kvanefjeld, where it occurs as a replacement mineral associated...

...Taghi Shirzad; Zaher‐Hossein Shomali AbstractAmbient seismic‐noise correlation is a powerful tool for extracting the seismic core phases that propagate through the interior of the Earth. In this study, we present and refine the root‐mean‐square‐stacking method to extract stable core phases (e.g...

... It is widely assumed that the boundary layer above the core is the source of intraplate volcanoes such as Hawaii, Samoa, and Yellowstone, and that the sub-plate boundary layer at the top of the mantle is thin and entirely subsolidus. In fact, this upper layer is thicker and has higher...

It is widely assumed that the boundary layer above the core is the source of intraplate volcanoes such as Hawaii, Samoa, and Yellowstone, and that the sub-plate boundary layer at the top of the mantle is thin and entirely subsolidus. In fact, this upper layer is thicker and has higher expansivity, buoyancy, and insulating power than the lower one, and may have higher potential temperatures. The observed seismic structure of the low-velocity zone (LVZ) including attenuation, anisotropy, sharp boundaries, and a reduction of both compressional and shear moduli can be taken as strong evidence for the ubiquitous presence of melt in the upper mantle. If the LVZ contains as little as 1%–2% melt, then it is the most plausible and accessible source for midplate magmas; deeply rooted active upwellings are unnecessary. The upper boundary layer is also the most plausible source of ancient isotopic signatures of these magmas and their inclusions.

... Near-vertical multiple ScS (S waves reflected at the core-mantle boundary) phases are among the cleanest seismic phases traveling over several thousand kilometers in the Earth's mantle and are useful for constraining the average attenuation and shear wave speed in the whole mantle. However...

Near-vertical multiple ScS (S waves reflected at the core-mantle boundary) phases are among the cleanest seismic phases traveling over several thousand kilometers in the Earth's mantle and are useful for constraining the average attenuation and shear wave speed in the whole mantle. However, the available multiple ScS pairs are limited. We took advantage of the recent dramatic increase in the number of global broadband stations and made a thorough computer-assisted search for high-quality data of multiple ScS pairs. We could find 220 station-event pairs which provided us with robust local estimates of average Q (quality factor) and two-way shear wave travel times. With the assumption that geometric focusing caused by lateral velocity heterogeneity does not seriously affect the amplitude measurements, the Q values exhibit strong short-range lateral variations, with very high and very low Q regions adjacent to each other. The mantle beneath seismic station KIP (Hawaii) has normal Q and shear wave speed, which supports the result of earlier studies. The mantle beneath station AFI (Samoa Islands) has a very high Q, possibly larger than 1400, and the slowest shear wave speed. The stations on the upper plate of the Tonga and Japan subduction zones yield average to low Q values. In contrast, the stations on the trenchward side of the upper plate of some subduction zones, e.g., station LVC (Chile) and station PET (Kamchatka, Russia), indicate high Q values, larger than 1000. We found no obvious correlation between Q and shear wave speed, which suggests that different factors like temperature, composition, anisotropy, etc., are controlling these properties in the mantle of different tectonic environments.

... represent core field characteristics and no crustal field effects (Finlay and Gillet, private communication, 2014). I subsequently used my SCHA model and calculated values for D, I and H at 0.5 degree intervals for the area between 25°S and 35°S and between 17°E and 32°E. Contour plots for D, I and H...

... iron + cohenite in basalt from Disko Island, Greenland. Such highly reduced conditions might have occurred early in the history of Earth; for example, according to the model of growth of the Earth’s core by Galimov (2005) , such conditions prevailed during only the first 100 million years...

...Cheng-Horng Lin AbstractBecause the Earth’s outer core is liquid, shear waves generated by a large earthquake that travel to the core (ScS) are totally reflected with strong seismic energy. It is interesting to note that one large aftershock (Mw 6.0) of the 2008 Wenchuan earthquake (Mw 7.9...

... Pacific, suggesting that hotspots are the surface expressions of mantle plumes originating from the deepest mantle. It is postulated that the apparent co-pulsations in magmatism result from global fluctuations in core-mantle interaction, involving periodic heating of Earth's core and subsequent increases...

...John A. Tarduno AbstractThe long-term history of the geodynamo provides insight into how Earth's innermost and outermost parts formed. The magnetic field is generated in the liquid-iron core as a result of convection driven by heat carried across the core-mantle boundary and freezing of the solid...

... provided unique opportunities for studying the magnetic field of the Earth’s core and its secular variation over the globe. The southern African continent (extending into the southern Atlantic Ocean) is an important area for such studies because of its intriguing field behaviour at both the Earth’s surface...

... 29.6° to 167.2°. Examination of travel times suggests these teleseismic P waves constitute the suite of body-wave arrivals from direct mantle P to outer- and inner-core reflected/refracted phases. The amplitudes of the teleseismic P waves also exhibit the typical solid-earth wave field phenomena of a P...

... to adequately represent the time-averaged field, the mean and range of values are similar to those of the present-day field. These values suggest that the inner core, which may stabilize the geodynamo, had started to grow by Early Proterozoic time. Unfortunately, Thellier data meeting laboratory reliability...

... islands of the St. Andrew Strait. This region of plume or hotspot 3He/4He ratios coincides with a domain of anomalously low seismic velocities at the underlying core-mantle boundary, and indicates that the provenance of high-3He/4He magmas in the Manus Basin (and possibly elsewhere) is linked...

...S. Houard; J. L. Plantet; J. P. Massot; H. C. Nataf AbstractThe purpose of this paper is 2-fold. It is first a continuation of the study of Massot and Rocard (1982) on the amplitude variations of the core waves near the PKP caustic, for French nuclear explosions in the South Pacific recorded...

...) comparable to that on the large debris flow, suggesting equivalent age.Pollen and plant macrofossils are described from a core taken in Seeley Lake. This core spans the period from ca. 9200 BP to the present. A disturbance event in 3380 ± 110 BP, correlative with the large Chicago Creek debris flow...